1. Field of the Invention
This invention pertains to multiple payload cartridges suitable for ejecting expendable payloads of chaff or the like and more specifically to such cartridges connectable for ejection ignition using two wires in the place of a minimum of three wires heretofore required.
2. Description of the Prior Art
A typical chaff dispenser carries 30 expendable payload units or cartridges, although dispensers having fewer and more than this number are also common. Each of such units is typically a square in cross section and about 8 inches long although other configurations exist. The payload may be chaff dipoles of varying lengths, although other expendable payloads suitable for operating in conjunction with cartridges hereinafter described include infrared flares, smoke producing payloads, photoflash plates, expendable jammers, propaganda leaflets, fertilizer, grass seeds and the like.
Each payload unit may be likened to a shotgun shell having an expendable payload which is ejected and having a liner which remains in the dispenser after the payload is ejected.
The dispensing mechanisms vary, but the most common type includes a pyrotechnic ejection system. Such a system uses an applied electrical signal to heat a bridge wire in a pyrotechnic gas generator referred to as a "squib" or sometimes as an "impulse cartridge". The heated, resistive bridge wire ignites the propellant charge in the ejection squib and the resultant gas pressure ejects the payload from the cartridge or unit. Thus, the system operates much like an electrically initiated shotgun shell.
The squib case holds all of the parts of the dispensing or ejection system and serves as electrical ground connection. The closure disc retains the propellant in the main chamber of the squib until the propellant is ignited, at which time the closure disc is ruptured by the gas pressure generated by the burning propellant. An electrical contact post, insulated from the squib case by a glass or plastic insulator, provides "hot wire" connection to an applied triggering current. The bridge wire is welded to the electrical contact post and to the squib case. Other squib configurations also exist.
When a proper electrical signal is applied between the electrical contact post and the squib case, the bridge wire is heated up and ignites the propellant. The burning propellant generates gas pressure which ruptures the closure disc allowing the gas to pressurize the volume underneath the piston in the payload liner. The piston transmits a pushing force to the payload and, therethrough, to the end cap. The end cap is forced out of the payload liner and then the payload is forced out of the payload liner (i.e., ejected) by the moving piston, which is also ejected.
The dispenser carrying the multiple cartridges are electrically connected so that each cartridge receives its signal, in turn, from an electrical contact of a "sequencer" switch, typically a rotary switch or equivalent, which moves from one position to the next.
Existing dispenser systems fall into one of two categories. The first category are those systems wherein a single expendable payload is put into each hole of the system. The second category are those dispenser systems that put multiple expendable payloads into each hole of the dispenser.
For the single-expendable-payload-per-hole dispenser systems, a common ground is normally employed for the cartridges, which is most often the chassis of the aircraft, or other vehicle. The connections to the sequencer switch include one hot wire running from a separate contact on the sequencer to each hole of the dispenser, thereby providing means for sequentially and separately electrically triggering the squibs. The sequencer, as noted above, functionally operates as a rotary switch with a movable contact that moves through the individual cartridge connections, providing firing current, one at a time, to each individual squib. The firing current heats the bridge wire to ignite the ejection charge, which causes ejection of the payload. Thus, one pair of electrical contacts is all that is required for each cartridge in such a system.
In the case of prior art dispenser systems using multiple expendable payloads per hole (cartridge), the wiring is more complex. For simplicity, assume only two payloads in each dispenser hole. In such case, a common ground may be employed; however, two "hot" electrical connections have heretofore been connected to each cartridge, one to the squib operating in conjunction with each payload. Therefore, two hot electrical connections or "firing" pins are required to each dispenser hole to make contact with the ignitors of the dual payloads. Hence, such a system is a three-wire system with three contacts for each hole (two hot connections and one ground connection). Such a system could also use one hot electrical connection and switch the ground between the squibs in the sequencer switch, but three wires would still be required to each hole.
Other variations in the prior art have included as many as four payloads stacked end-to-end in each hole. As can be seen, this has required at least five electrical contacts (four hot contacts and one common ground) for each hole.
As technology has advanced, it has become possible to achieve the desired expendable payload characteristics with smaller expendables. For example, if two expendables could be installed in the place of one, system effectiveness would be vastly increased since more expendables could be carried in the same dispenser volume. In order to minimize modification of existing dispensing systems, it is preferable to avoid physically modifying the dispenser units and aircraft wiring and to instead modify the dispenser electronics (e.g., the sequencer electronics) and/or the expendable unit electronics (i.e., the squib-related electronics) to allow two-wire operation for separately igniting the multiple payloads in a single cartridge.
Therefore, it is a feature of the present invention to provide an improved multiple payload cartridge input connection for separate ignition of the payloads therein using only two wires for connection thereto.
It is another feature of the present invention to provide an improved multiple payload cartridge having means for ensuring against the simultaneous ignition of the squibs therein by a single applied electrical pulse, and having means for igniting squibs individually upon command.